Novel paper sizing agents



NOVEL PAPER SHZENG AGENTS Erhart K. Drechsel, Springdale, and Randall Hastings and Edward Strazdins, Stamford, Conn., assignors to Amerm ican Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application June 3, 1953, Serial No. 359,432

The present invention relates to the manufacture of fortifying rosin sizes or soaps useful in the manufacture of sized paper and for other purposes. More particularly the present invention relates to the manufacture of fortifying rosin sizes wherein a reaction product is formed v corresponding to that formed by the coreaction of rosin,

maleic anhydride, and a lower alkanol, and a sizing solu tion is made therefrom by saponifying the reaction mixture with a hot aqueous alkali metal alkali solution at atmospheric pressure, that is, at temperatures below the normal boiling point of such solutions. The invention includes the step or forming a mixture of fortiiied sizes either by mixing molten rosin with theaforementioned reaction mixture and saponifying the mixture, or by any equivalent method.

Rosin may be reacted with up to one mol of maleic anhydride or with known equivalents (hereinafter included in the term maleic anhydride) to form a Diels- Alder reaction product or adduet, hereinafter termed maleated rosin which, when reacted or saponiiied with an aqueous alkali such as aqueous sodium hydroxide acts as an adjuvant or fortifier for ordinary rosin size. The presence of a minor proportion of maleated rosin size in ordinary rosin size permits formation of sized paper having superior resistance to water and other liquids as compared with the resistance imparted by an equal weight of the rosin size alone.

When up to 7% (0.21 mol) of maleic anhydride is used, based on the weight of the rosin, the maleated rosin has a low softening point and can be readily formed into a homogeneous sizing solution by cooking with hot aqueous caustic solution at atmospheric pressure at temperatures slightly below the boil.

Rosin may also be reacted with more than 7% of its rates Patent disadvantage in the manufacture of weight of maleic anhydride, the products obtained by reacting rosin with S%-l0% ot' its weight of maleic anhydride. however, being increasingly difficult to saponify by the method described.

When, however, rosin is reacted with 10% of its weight of maleic anhydride, corresponding to 0.3 mol of maleic f anhydride per mol of rosin, the reaction product cannot be homogeneously saponiiied at atmospheric pressure by any practical means. Such maleated rosins have softening points so high that when cooked with aqueous caustic as close to the boil as control of foaming will permit, they form large solid masses only the surfaces of which are saponitied. Maleated rosins of this type can be saponitied only by cooking with aqueous caustic solution in an autoclave at temperatures well in excess of 100 C., the solution being maintained under suicient pressure to permit the necessary temperatures to be reached.

Typically, when fully maleated rosins are saponitied, solution temperatures of 150 C.200 C. are required necessitating autoclave pressures up to 90 lbs. per sq. inch. Rosin size is manufactured industrially in verylarge quantities and the cost of autoclave equipment large enough to accommodate the quantities involved, together with the heat requirements thereof, constitutes a serious tion containing any desired proportion of the maleated lgatented May 7, 1957 rosin size by this method.

Maleated rosins which have softening points below C., asdetermined by the capillary tube method, are readilysaponiied at atmospheric pressure. The higher softening point maleated rosins are increasingly diiiicult to saponify, and C. is taken as representative of the maximum softening ypoint which a maleated rosin may have and yet be saponiable at atmospheric pressure in present-day industrial equipment.

From the foregoing it will be seen that need for pressure saponiication can be obviated by partially maleating the rosin, that is, by maleating the rosin with less than 7% of its weight of maleic anhydride. Rosin maleated to this and lesser extents can be saponiiied at atmospheric pressure quite readily. In such event, however, not more than about 0.21 mol or 21% of the rosin undergoes the reaction, the remainder (0.79 mol or 79%) of the rosin passing through the reaction substantially unchanged. Thus when proceeding according to this method there is a very significant waste in heat, labor, and utilization of equipment.

The discovery has now been made that maleated rosins partially esteritied with a lower alkauol, the weight of the alkanol being at least 2% of the weight of the rosin, and containing more than 0.3 mol of combined maleic anhydride or the equivalent, may readily be prepared in a form having softening points below about 85 C. and that homogeneous and very eliective fortifying solutions are readily prepared when such esteriiied maleated rosins are at least partially neutralized with a caustic saponifying solution at atmospheric pressure at temperatures higher and preferably about 15 C. higher than their softening points. Y

The further discovery has been made that fully maleated esteried rosins, that is, rosins containing Aeven substantially their full theoretical equivalent of maleic anhydride, and esteriiied as hereinafter'described, have sirnilarly low softening points and may be saponiiied in similar manner at atmospheric pressure'with similar results.

We have found that the fortifying agents thus prepared may be mixed with liquid rosin size and that the mixture so prepared is a fortified size having substantially the same sizing eiiectiveness as rosin size which has been fortified in the same manner with maleated rosin prepared by the direct reaction of rosin with maleic anhydride.

From the foregoing it will thus be seen that the principal feature of the present invention is the reaction of rosin with between about 0.3-0.4 and 1 mol of maleic anhydride or its equivalent, taking the molecular weight of rosin to be 302, and a small amount, at least 2% based on the weight of the rosin, of a lower alkanol to form a partially esteried maleated rosin having a softening point below about 85 C. and saponifying the partially esteriiied maleated rosin at atmospheric pressure with hot aqueous alkali metal alkali solution having a temperature at least 15 C. higher than the softening point of the maleated rosin to form a homogeneous liquid fortifying sizing solution.

In addition to permitting saponiication at atmospheric pressure, the present invention possesses other important advantages.

In the first place the partially esteriiied maleated rosin itself may be prepared under atmospheric pressure, without need for lhigh pressure reaction equipment.

Finally, the present invention permits rosin in liquid form, at a comparatively low temperature, toy be mixed with the partially esteriiied maleated rosin, and further permits the mixture to be saponiiied in the manner described, lthus yielding in one step a fortified sizing solurosin.

The benets of the present invention continue to increase as the ratio of maleic anhydride rises from 0.3 mol to its theoretical maximum of one mol per mol of rosin. As a practical matter, it is diicult to cause the last traces of maleic anhydride to react. with the rosin when the former is present at its theoretical maximum ratio. In practice it is therefore preferred to employ about 0.7 to 0.9 mol of a maleic anhydride per mol of rosin, this proportion of maleic anhydride permitting the benefits of the present invention to be substantially attained while minimizing the amount of unreacted maleic anhydride or the equivalent carried into the product.

The amount of alcohol which should be added in each instance depends principally on the particular alcohol selected, the temperature of the reaction and the softening point which is desired to impart to the adduct. The effect of the various alcohols in depressing the softening point does not appear to be related directly to their molecular weight, and hence the proportions are best expressed in terms of the weight of the alcohol based on the weight of the rosin. Good results have been obtained when as little as 2% of alcohol is present in esterilied form based on the weight of the rosin, equivalent to 1.6% based on the weight of fully maleated rosin. Very satisfactory results have been obtained by using from this amount up to 6%-8%, based on the weight of the rosin, this amount generally giving an adduct which softens in the range of 70-85 C.

The addition of this or a greater amount of alcohol does no harm, but causes a further depression in the softening point which is unnecessarily great for practical purposes. Any unreacted alcohol remaining can be recovered by distillation. Alternatively, the unreacted alcohol may be allowed to remain in the reaction mixture where it will beneficially decrease the viscosity of the sizing solution prepared.

The correct amount in each instance to produce an adduct having the desired softening pointvcan best be determined by making a series of simple laboratory trials, maintaining all conditions constant except the amount of alcohol.

The reaction described above may be performed. by a number of different procedures, all essentially equivalent and each thus constituting a different aspect of the invention. f

According to one procedure, the reaction may be performed in two separate steps. In the first step, rosin is reacted with the maleic anhydride. In the second step, the product is heated with the alkanol to form the partially esteriled reaction mixture described. The reaction is continued in the presence of the alkanol until a reactionproduct is obtained having a softening point beklow 85 C.

According to the second method, also a two-step method, rosin is esteried with the requisite amount of the alkanol. and the resulting partially esteried rosin is heated with the maleic anhydride until substantially all of the maleic anhydride has reacted.

In industrial practice, it will undoubtedly be preferred to prepare the reaction product by a one-step method. This may be done by mixing the rosin with the maleic anhydride and the alkanol and reuxing the mixture at 160 C. to 210 C. both until reaction of the maleic anhydride with the rosin is substantially complete and a partially esteritied reaction mixture results having a softening point below 85 C.

Any unreacted allianol may be removed by distillation, or the alcohol may be allowed to remain. In this reaction it is probable that a proportion of the alkanol reacts at once to form a monoalkyl maleate, and hence this material may be used to replace all or part of the maleic anhydride and alkanol.

Other methods of preparing the above-described partially esteriiied maleated resins will occur to those skilled in the art. i

The softening points referred to in the specification and the claims are those determined by the standard capillary tube method, wherein the maleated rosin is finely crushed, mixed with a trace of an oil-insoluble dye such as Helmerco green BCG, and the powder placed in a capillary tube and the tube is placed in a hot water bath. In making the determination the softening point l is taken as occurring at the temperature where the white powder begins to melt and to form droplets of colored liquid.

Formation of the partially esteritied reaction products of the present invention takes place satisfactorily at any temperature from about C.-220 C. and normally requires about 7 hours at the lower temperature and about l to 2 hours at the higher temperature. When thc upper temperature is materially exceeded, an effect takes place, the nature of which is not understood, but which results in the development of a size of inferior quality. Below about 160 C. the reaction proceeds very slowly, making these lower temperatures uneconomic.

The reaction itself is preferably performed in a reux vessel at atmospheric pressures. lt may, however, be performed in an autoclave under autogenous pressure, and this permits somewhat less alcohol to be used.

Saponification of the partially esteriied maleated rosins described may be performed by any of the methods normally employed for saponifying ordinary resin. For example, the reaction mixture may be flowed with hot caustic solution into a conventional cook tank, or the caustic solution may be stirred into the reaction product in the reaction vessel itself. Neither the amount nor strength of the alkali metal base solution plays any part in the present invention. Normally, however, the solution will contain about 20% caustic by weight and sufficient of` the reaction mixture will be saponiiied to provide a sizing solution containing more than 50% solids.

The temperature of the saponication should be not less than the softening point of the resins as determined by the capillary tube method, and in general, the higher the temperature the more rapid the saponication. Preferably the caustic solution will be at least 10 C. above the softening point of the rosin, this temperature providing `a fluid melt, and most advantageously will be as hot as possible consistent with tolerable development of foam. This is usually a few degrees below the boil. For example, in the case of soda ash and sodium hydroxide solutions, the preferred temperatures are within the range 92 C.-96 C., saponication taking place within this range with maximum rapidity yet with development of 4little foam.

Still alternatively, cool caustic solution may be mixed with the adduct in the solidified state and heated. Saponcation begins when the temperature of the mixture is substantially equal to the softening point of the adduct.

The amount of caustic may be varied from that sufficient to produce a partially neutralized size preferred by paper manufacturers when the size is to be ladded directly to the beater, usually 50%-80%, to that suicient to provide a substantially completely neutralized size, preferred when the size is to be transported in dry form.

It is not essential to use maleic anhydride in the synthesis. In its place, any equivalent material may be ernployed, for example, any material which forms maleic anhydride when heated to reaction temperatures. lncluded among the latter are maleic acid, land the half esters thereof. Fumaric acid and its half esters yield corresponding products.

As alkanols may be employed any allranol containing not more than 5 carbon atoms, that is, methanol, ethanol, propanol, sopropanol, butanol, the isobutanols, amyl alcobol, and the isoamyl alcohols. All these alcohols yield very similar results on a weight for Weight basis, and it is therefore apparent that the choice of alkanol is not critical, anylower alkanol being suitable..

1n, practice we prefer to employ the intermediate alsporgere eohols particularly the propanols. Retention of these alcohols in the reaction mixture is readily controlled by ordinary reux equipment yet they can be readily stripped off when present in excess. Moreover, these alcohols act as an excellent viscosity depressant for the final size when the excess is allowed to remain in the mixture.

As saponifying agents any alkali metal alkali may be used including sodium hydroxide, sodium bicarbonate and sodium carbonate. The corresponding potassium salts may also be used, and these give somewhat better results when the saponitied product is to be used as a foaming agent in the manufacture of gypsum board.

The saponied fortifying adducts of the present invention find their principal use in the manufacture of sized paper by the beater addition process. A stock of papermaking cellulosic fibers is formed at a consistency of about 0.5% to about 4% and to this is added between about 1A and 4%, based on the dry weight of the fibers, of the saponifed reaction mixture, preferably diluted to about 5% solids concentration. Suicient `alum is then added to precipitate the size, typically 1 to 1.5 times the weight of the size, after which the fibers are sheeted and dried to form paper.

More advantageously, in place of the saponited fortifying adduct referred to there will be added a mixture composed of the saponiiied reaction mixture and rosin size, in which event the former acts as a fortifier for the latter. Best results from the point of view of sizing imparted are obtained when the weight of the rosin size is 3 to 4 times the weight of the fortifying size, but very good results are obtained when the fortifying size is from about to 50% of the mixture. Thus the mixture may advantageously contain from 10% to 50% by weight of the fortifying adduct. The total weight of the mixture of sizing `agents added should be between about 1A and 4% of the dry weight of the fibers. l

The invention has been completely disclosed above. The following examples illustrate specific embodiments of the invention and are not to be construed as limitations thereon. Parts are by weight unless otherwise stated.

Example 1 A mixture of 453 g. (1.5 mols) of N-grade rosin and 205 g. (1.5 mols) of 95 monomethyl maleate was charged into a laboratory tiask fitted with stirrer, thermometer and take-off condenser, heated at 195 -200 C. for 2 hours and cooled. A sample was found to have a softening point of 77 C. by the capillary tube method. Calculations based on the weight of methanol evolved indicated that the product contained 20.8% of the methanol present in the maleate, equivalent to 0.313 mol of methanol in esteried form.

500 g. of the product was melted over an oil bath at 105-ll0 C. This was added to 540 gm. of a hot NaOH solution `at 95 C. A homogeneous, well saponiiied fortifying sizing solution was obtained by slowly stirring the mixture for 2 hours at that temperature. Hot water was then added to adjust the solids content to 50%.

A comparative experiment was made by mixing 453 gm. of the same rosin with 147 gm. (1.5 mols) of maleic anhydride and reacting the two in the same apparatus for 2 hours at 195 C.-200 C. The maleated rosin thus formed had a capillary tube softening point of 93 C. and could not be saponied when heated with 25% NaOH in the same manner. As a result of its high softening point the product was a lumpy mass, the lumps being saponilied only on the outside.

Example 2 The procedure of Example 1 was repeated using however 227 g. (1.5 mols) of 95% monoethyl maleate in place of the 1.5 mols of monomethyl maleate. The product had a softening point of less than 70 C. and con- 6 tained 31.8% of the alcohol present in the maleate ester, equivalent to 0.48 mol of esterilied ethanol. 'I'he product was equally satisfactorily saponilied at the same temperature using soda ash solution.

Example 3 Example 4 The procedure of Example 1 was repeated using 249.5

g. (1.5 mols) of mono-n-propylmaleate in place vof the 1.5 mols of monomethylmaleate. The product had a softening point of less than 70 C. and contained 37.2% of the esteriiied propanol, equivalent to 0.55 mol of propanol based on the rosin used. The product was equally readily saponilied.

Example 5 Into a 10G-gallon steam jacketed kettle equipped with agitator and with a water-cooled reflux and takeoff condenser was charged 198.5 lbs. (0.66 mol) of gum rosin, and steam was passed into the jacket. When the rosin was fluid, 51.5 lbs. (0.525 mol) of maleic anhydride was added and the condenser set for total reflux. With the charge at C. 17.5 lbs. of isopropanol (0.445 mol) was then run in causing the temperature of the mixture to rise to 165 C. as adduct formation and esterication took place. The mixture was reuxed for 7 hours resulting in formation of a partially esteried maleated rosin having a softening point of 74 C.

Heating ywas then discontinued. 58 lbs. of sodium hydroxide as a 19.4% aqueous solution was then added, the solution being added very slowly at lirst to avoid overloading the condenser. After all the caustic had been added, the mixture was stirred at 92-95 C. for 2 hours. A homogeneous fully saponiied fortifying sizing solution was obtained which was free from lumps, which had a solids content of 53.5% and which had a pH of 9.

Example 6 The procedure of Example 5 was repeated except that the method of saponilication was reversed. The caustic solution was prepared in a closed vessel provided with steam coils, condenser andl stirrer and was heated to 94 C. The partially esteriiied maleated rosin was allowed to flow into the caustic solution slowly. After all the maleated rosin had been added, the sizing solution was cooked 4at 90-95 C. for one hour. During the cooking a part of the esterified isopropanol was hydrolyzed. The sizing solution obtained was substantially identical with the solution of Example 5.

Example 7 14,800 pounds of sizing solution prepared according.

to Example 6, having a solids content of 59% and a ternperature of 70 C. and 25,000 pounds of tall oil rosin at C. were simultaneously added to a reaction tank equipped with heating coils and agitator. The mixture was maintained at 100 C. until homogeneous and a solution at 95 C. of 1650 pounds of caustic soda dissolved in 5,000 pounds of water added to saponify the tall oil rosin. The reaction mixture was held at 95 100 C. for l hour. The product, a mixture of maleated rosin size and tall oil rosin size, was then cooled and 375 pounds of isopropanol added to reduce its viscosity.

Example 8 3,020 lbs. of gum rosin (10 mols) was charged into a steam-j acketed kettle equipped with agitatoL, a watercooled redux and take-off condenser, and melted. To this was added a solution of maleic anhydride in ymonoisopropyl nialeate prepared by dissolving 347 lbs..of maleic anhydride (3.55 mols) in 693 lbs. of monoisopropyl maleate (5.3 mols). The mixture was heated to 160 C., agitation being assisted by circulation of the mixture. lsopropanol was liberated soon thereafter and was reiluxed for 2 hours. The condenser was then set for isopropanol take-o, and 60 lbs. was collected. The reaction was continued for a total of 7 hours at 160 C. giving an adduct having a softening point of 75 C.

To the reaction product was added 890 lbs. of sodium hydroxide (22. mols) dissolved in 3190 lbs. of water, the addition being made slowly at rst until evolution of steam had moderated. The solution was stirred for l hour under reflux to minimize loss of water at 90 C. The pH of the size thus prepared was about 9.2 and its solids content about 55%. It was substantially identical with the solution of Example 5.

Example 9 250 lbs. of gum rosin (0.82 mol), 65 lbs. (0.66 mol) of maleic anhydride and 14.3 lbs. (0.24 mol) of isopropanol were run into an autoclave and the mixture heated to about 165 C. and maintained at that temperature under autogenous pressure for 7 hours. The product which had a softening point of 81 C. was slowly run into a solution of 80.4 lbs. (2 mols) of lsodium hydrox'ide in 215.5 lbs. of water at 95 C. with agitation, and stirred at that temperature for one hour. The caustic solution was in a vessel provided with a steam condenser and the condensed steam was returned to the solution. The solids concentration of the size thus prepared was 62.1%. It was substantially identical with the solution of Example 5.

We claim:

l. A process for manufacturing a rosin size fortifying agent which includes the steps of coreact-ing at about l60220 C. one mol of rosin, 0.3 mol to l mol of maleic anhydride, and at least 2% of a lower` alkanol based on the weight of the rosin to form a partially esteriiied maleated rosin having a softening .point below 85 C. and saponifying said maleated rosin at atmospheric pressure with hot aqueous alkali metal alkali solution having la temperature higher than the softening point of said ma-leated rosin.

2. A'process' for manufacturing a rosin size fortifying agent which includes the steps of coreacting at about --220f7 C. one mol of rosin with 0.3 mol to 1 mol of a mixture of maleic anhydride and a lower alkyl monoester of maleic acid, the alkanol thus esteriied being at least 2% of the'w'eight of the rosin, lto form a partially esteriledmaleated rosin having a softening point 4below 85 C., and saponifying said maleated rosin at atmospheric pressure with hot aqueous alkali met-al alkali solution having, a temperature at least about 15 C. above the softening point of said maleated rosin.

3. A process. for manufacturing a rosin size fortifying agent which includes the steps of csterifying a lower lalkanol with 'a material corresponding to the condensation product of rosin with 0.3`rnol to l rn-ol of maleic anhydride to form a partially esterified maleated rosin having a softening point below 85 C., and saponifying said rosin at atmospheric pressure with hot aqueous alkali metal `alkali solution hav-ing a temperature atleast about 15 C. above the softening point of said partially esteried maleated rosin.

4. A process yaccording to claim l wherein the coreactants are reuxed at atmospheric pressure.

5. A process according toelaim l wherein the alkanol is a propanol.

l6. A process according to claim 1 wherein the aqueous alkali metal alkali is aqueous sodium hydroxide.

7. A process according to claim 1 wherein the amount of maleic anhydride is between 0.7 and 0.9 mol per mol of rosin.

8. A process according to claim 2 wherein the Aamount of mixture of ma-l'eic anhydride and a lower alkyl monoester of maleic acid is between 0.7 and 0.9 mol per mol of rosin. v

9. A process according to claim 3 wherein the amount of maleic anhydride is between 0.7 and 0.9 per mol `of rosin.

References Cited in the file of this patent UNITED STATES PATENTS 2,081,889 4Borglin May 25, 1937 2,447,750 Harris Aug. 24, 1-948 2,465,888 Lawrence Mar. 29, 1949 2,628,918 Wilson et al. Feb. 17, 1953 

1. A PROCESS FOR MANUFACTURING A ROSIN SIZE FORTIFYING AGENT WHICH INCLUDES THE STEPS OF COREACTING AT ABOUT 160*-220*C. ONE MOLE OF ROSIN, 0.3 MOL TO 1 MOL OF MALEIC ANHYDRIDE, AND AT LEAST 2% OF A LOWER ALKANOL BASED ON THE WEIGHT OF THE ROSIN TO FORM A PARTIALLY ESTERIFIED MALEATED ROSIN HAVING A SOFTENING POINT BELOW 85*C. AND SAPONIFYING SAID MALEATED ROSIN AT ATMOSPHERIC PRESSURE WITH HOT AQUEOUS ALKALI METAL ALKALI SOLUTION HAVING A TEMPERATURE HIGHEE THAN THE SOFTENING POINT OF SAID MALEATED ROSIN. 